The invention relates to pharmaceutical compositions comprising (1) a solid amorphous dispersion comprising a low-solubility drug and a concentration-enhancing polymer and (2) a lipophilic microphase-forming material that enhances the concentration of the drug in a use environment.
Low-solubility drugs often show poor bioavailability or irregular absorption, the degree of irregularity being affected by factors such as dose level, fed state of the patient, and form of the drug. Increasing the bioavailability of low-solubility drugs has been the subject of much research. Increasing bioavailability depends on improving the concentration of dissolved drug in solution to improve absorption.
It is well known that the amorphous form of a low-solubility drug that is capable of existing in either the crystalline or amorphous form may temporarily provide a greater aqueous concentration of drug relative to the equilibrium concentration obtained by dissolution of the drug in a use environment. Such amorphous forms may consist of the amorphous drug alone, a dispersion of the drug in a matrix material, or the drug adsorbed onto a substrate. It is believed that such amorphous forms of the drug may dissolve more rapidly than the crystalline form, often dissolving faster than the drug can precipitate from solution. As a result, the amorphous form may temporarily provide a greater-than equilibrium concentration of drug.
While such amorphous forms may show initially enhanced concentration of the drug in a use environment, nevertheless the improved concentration is often short-lived. Typically, the initially enhanced drug concentration is only temporary and quickly returns to the lower equilibrium concentration.
One approach to increase the bioavailability of low-solubility drugs has involved forming amorphous dispersions of drugs with polymers. Examples of attempts to increase drug concentration by forming a dispersion of the drug with a polymer include Nakamichi et al., U.S. Pat. No. 5,456,923, and Curatolo et al., EP 0901786A2.
It is known to mix surfactants with solid amorphous dispersions. Curatolo et al., EP 0901786A2 disclose that a component of the dispersion may be a surface-active agent such as a fatty acid and alkyl sulfonate, commercial surfactants such as benzethanium chloride, docusate sodium, and polyoxyethylene sorbitan fatty acid esters, and natural surfactants. Curatolo et al. state that such materials can advantageously be employed to increase the rate of dissolution by facilitating wetting, thereby increasing the maximum drug concentration and the degree of supersaturation attained, and also to inhibit crystallization or precipitation of drug by interacting with dissolved drug by mechanisms such as complexation, formation of inclusion complexes, formation of micelles or adsorbing to the surface of solid drug, crystalline or amorphous. Curatolo et al. state that these surface active agents may comprise up to 25% of the dispersion. In addition, Curatolo et al. also disclose that surface active agents may be present in compositions containing dispersions.
Nevertheless, what is still desired is a composition that may enhance the dissolution and/or bioavailability of poorly soluble drugs. These needs and others that will become apparent to one of ordinary skill are met by the present invention, which is summarized and described in detail below.